Transplantation of embryonic neural tissue to the central nervous system of brain damaged adult host rats has been demonstrated to induce anatomical indices of reinnervation, biochemical indices of neurotransmitter restoration and behavioral indices of functional recovery. Aged rats exhibit specific anatomical, biochemical and behavioral deficits in systems that have been previously demonstrated by this laboratory to respond favorably to transplantation of embryonic neural tissue in the adult host rat. We propose to determine 1) if the aged rat will act as a receptive host of transplanted embryonic neural tissue, and 2) whether the transplants will reverse the behavioral deficits measured. Further experiments will determine 1) the optimal parameters of transplantation, 2) whether transplantation at an earlier date will protect the development of aged related deficits and, 3) whether multiple grafts are more effective than single grafts. Subsequent experiments will test 1) effectiveness of embryonic nerve cells in other brain areas, 2) combined effect of drug treatments and transplants and 3) the effectiveness of cross-species transplantation. We will use histochemical methods to determine the extent of anatomical innervation, biochemical markers as indices of neurotransmitter restoration, and behavioral tests as indices of functional recovery. The overall objective of the research is to introduce the transplantation techniques into the ongoing investigation of aging as a new tool to determine basic mechanisms underlying the aging process.